The Roles of Socioeconomic Status, Occupational Health and Job Rank on the Epidemiology of Different Psychiatric Symptoms in a Sample of UK Workers.

There is a considerable gap in epidemiological literature about community mental health showing how psychiatric symptoms are associated with job rank, socioeconomic status, and occupational health. We examine data from 4596 employees collected in the United Kingdom's Psychiatric Morbidity among Adults Living in Private Households Survey. There were 939 workers in managerial jobs, 739 in supervisory jobs and 2918 employees in lower ranking jobs. Of the 4596 workers, 2463 had depressive symptoms and 2133 no depressive symptoms. Job rank, household gross income, social class, personal gross income and socio-economic group were significantly associated with general health, occupational health and depressive and avoidant symptoms. Job rank, occupational and physical health also explained the variance in paranoid and avoidant symptoms among the employees. This study shows that severe psychopathology is related to workers' job rank.

Radiocarbon dating of East african lake levels.

The fluctuations of the key East African lakes discussed are summarized in Fig. 4 which also includes the available evidence from Lake Rukwa (42) and Lake Chad (43) Exceot for Lake Victoria, all of these now lack surface outlets and are situated in much drier climates than the major lakes of the Western Rift Valley, which remain filled to their overflow levels. The apparent differendes among the fluctuations of the lakes are partly due to differendes in the nature of the evidence or the intensity of research or both, although there must also have been important local differences in the histories of the lakes Yet the consistencies are far more striking, most notably the coincidence of early Holocene high stands. Between 10,000 and 8,000 years ago, it seems that lakes in many parts of tropical Africa were greatly enlarged. Where evidence for the previous span of time is well resolved, it appears that transgressions leading to this high stand began about 12,000 years ago, and evidende from three basins (Victoria, Nakuru, and Chad) indicates a pause or minor recession just at or before 10,000 years ago. Wherever information is available for the period preceding 12,000 years ago, it can consistentlybe shown that lakes were much small-er . Several basins (Rudolf, Nakuru, and Chad) also show traces of much earlier phases of lake expansion. which are not yet well dated but which all occurred more then 20,000 years ago. The Holocene record subsequent to the maximum of 10,00 to 8,000 years ago is more complex. Three basins (Rudolf, Nakuru, and Chad) show an apparently concordant, positive oscillation at some point between 6000 and 4000 years ago, but it is uncertain how widely this episode is represented. Although many of these lakes that are now closed filled to overflowing at least once during the late Quaternary, it is evident from Fig. 4 that the periods of expansion were short-lived compared with phases of contraction to levels near those of today. This pattern may be in accord with fragmentary evidence from lower and middle Pleistocene formations, such as those of Olduvai(44)and Paninj (45), within which some relatively short-term lake expansions can be documented, but which lack evidence for any marked long-term departure from a balance of evaporation and precipitation similar to the present one Further, this pattern of brief moist pulsations, with a duration of perhaps 2000 to 5000 years, is also suggested by other late Pleistocene and Holocene sequences (based primarily on geomorphological and palynological evidence) from the Saharan area, Angola, and South Africa (46). In default of radiometric dating, such complex successions of relatively brief moist intervals provide few stratigraphic markers of broad applicability. This, together with the fact that vegetation, weathering processes, montane glaciers, lake size, lake salinity, and so forth are all likely to reflect the diverse aspects of Climatic change differently, underscores the strictures of Cooke (2) and Flint (3) against the use of pluvials and intrlvasas a basis for subdividing Quaternary time in Africa. Positive correlations between high-latitude glacial advances or maxima and intervals of high lake levels have been demonstrated or suggested for many areas of mid-latitude North America and Eurasia (47), and similar patterns have often been regarded as probable for tropical Africa as well. However, the evidence summarized above shows a notable lack of such correlations for the tropical lakes considered here. If glaciation and tropical lake levels were connected at all, then a far more complex-delayed, multiplefactor, or inverse-relationship must be sought for the late Quaternary (48). This renders the introduction of new climato-stratigraphic terms such as hypothermal and interstadial (49) of questionable value in East Africa. Further, whereas the so-called pluvial lakes of higher latitudes were probably due primarily to reduced evaporation (50), our computations for the early Holocene lakes Nakuru and Naivasha, as well as for the oscillations of Lake Rudolf and Lake Victoria in recent decades, suggest that many or most of the high tropical lake levels where associated with a modest but significant increase in precipitation.

Characterisation of Leishmania isolates from Laikipia District, Kenya.

Using cloned kDNA sequences from the reference strain of Leishmania tropica IC-067, we have screened leishmanial isolates from Laikipia District of Kenya and identified these isolates as L. tropica. One isolate, IC-331, from a rat (Rattus rattus) was typed as L. tropica. This is the first time that L. tropica has been isolated from a wild rodent in Kenya and thus the first indication that the disease caused by L. tropica might be a zoonosis. The leishmanial isolates, especially those of sandflies, display extensive heterogeneity, prompting a need for selecting local and/or regional reference strains to generate species-specific DNA probes for use in identifying field isolates.

Effect of controlled burning on survival of floodwater Aedes eggs in Kenya.

The effect of controlled burning on the survival of Aedes mosquito eggs was evaluated in 2 distinct dambo habitats. In a dambo dominated by grasses, egg survival was 3.3% after burning compared with 43.8% in a similar dambo that was not burned. In a dambo dominated by sedges, egg survival was 0.7% after burning compared with 28.5% in a similar dambo that was not burned. Mortality of mosquito eggs appeared to be caused by high temperatures associated with the fire and not elapsed time since egg survival did not decrease with time after burning. The potential for burning to control the mosquito vectors of Rift Valley fever virus is discussed.

Pretreatment of floodwater Aedes habitats (dambos) in Kenya with a sustained-release formulation of methoprene.

Effectiveness of sustained-release Altosid pellets (4% AI methoprene) against floodwater mosquitoes in dambos treated at 5, 3, and 1 wk before and 1 day after flooding was determined. Only 2% of Aedes pupae (primarily Aedes mcintoshi) survived to adults in an area treated 5 wk preflood, and no adult mosquitoes emerged from an area treated 1 day after flooding. In contrast, 12 and 16% of Aedes pupae successfully survived to the adult stage in areas pretreated 3 and 1 wk, respectively, preflood. The effectiveness of the Altosid declined against Culex spp. (primarily Cx. antennatus) collected from dambos 15-31 days after flooding. The potential for using preflood treatment with methoprene to control Aedes vectors of Rift Valley fever virus in endemic areas is discussed.

Epidemiology of leishmaniases in Kenya. Natural host preference of wild caught phlebotomine sandflies in Baringo District, Kenya.

Host preference of wild caught phlebotomine sandflies was studied in Marigat, Baringo District, Kenya, an endemic focus for both Leishmania donovani Laveran & Mensel and L. major Yakimov & Schokhov using precipitin test of blood meals. Sandflies of the Phlebotomus Rondani & Berte and Sergentomyia Franc & Parrot genera were encountered blood fed and resting in nine different habitats which were investigated. Analysis of their blood meals revealed a distinct host preference between the Phlebotomus and Sergentomyia genera. A distinction of host preference within species of each of the two genera was also observed. Furthermore, certain resting habitats from which the bloodfed sandflies were collected appeared to be favoured by specific sandfly species. It was observed that most of the wild hosts such as lizards and rodents except the hippopotamus, shared the same resting habitats with the sandflies. It was also observed that the man-biting sandflies preferred to rest outdoors after feeding. Domestic animals and man were the favoured hosts of vectors of both visceral and cutaneous leishmaniases, thus introducing an element of zooprophylaxis.

Epidemiology of leishmaniases in Kenya: V. Wider search for breeding habitats of phlebotomine sandflies in three kala-azar endemic foci.

Intensive investigations on the breeding sites of phebotomine sandflies were undertaken in Kitui, Machakos and Baringo foci of leishmaniases in Kenya. A total of 473 soil samples weighing approximately 4,244 kg were collected from termite hills, animal burrows, tree hole, human dwellings, animal enclosures, under tree canopy, open ground, chicken coop and rock crevices habitats and incubated in the field laboratories. 267 samples weighing approximately 3002 kg were positive, producing 6419 sandflies comprising 17 different species. This study resulted in the identification of both perennial and seasonal breeding sites of most of the phlebotomine sandfly species found in these three leishmaniases foci.

Studies on the epidemiology of leishmaniasis in Kenya: flight range of phlebotomine sandflies in Marigat, Baringo District.

A study on the flight range of phlebotomine sandflies using the mark-release-recapture technique was undertaken in Marigat, Baringo District, Kenya, to determine the distance sandflies are able to travel and assess their importance in disease transmission. Over a period of 17 months, a total of 108,429 sandflies collected from their natural habitats were marked and released from a central point in a valley. Of these, 842 (0.8%) sandflies comprising 11 species were recaptured. Ninety-five percent of the recaptured sandflies were recovered within a radius of 50 m from the release point and 54% within a radius of 10 m. Two Sergentomyia ingrami females were recaptured at a distance of 1000 m from the release point.

Choice of resting sites by Anopheles gambiae (Diptera: Culici) in Mwea Rice Irrigation Scheme, Kirinyaga District, Kenya.

Investigations on Anopheles gambiae were carried out in Mwea Rice Irrigation Scheme, Kenya, to determine their preference for resting on various colours of fabrics and bare walls inside rural houses. The inside wall surface of each house was divided into upper, middle and lower sections and the section further partitioned into subsections measuring 0.6 x 0.3m. Two sets of experiments were conducted: one in which the walls were partly fitted with one colour of fabric at a time (double-choice situation), while in the other the walls were fitted with a combination of six colours (red, black, yellow, white, green and blue) of fabric at once, (multiple-choice situation). The number of mosquitoes resting on each of the pieces of cloth pinned to the walls and the uncovered subsections of the wall were recorded for each section of the wall after 24 hours. The results showed resting preference for cloth covered parts of the walls. The white colour was found to best attract mosquitoes followed by colours red, yellow, black, blue and green. The hanging strips in the middle of the houses had fewer mosquitoes resting on them than those on the wall.

Cutaneous leishmaniasis in Kenya: Sergentomyia garnhami (Diptera Psychodidae), a possible vector of Leishmania major in Kitui District: a new focus of the disease.

Investigations on phlebotomine sandflies in Tseikuru, Kitui District, Kenya were carried out to determine the vectors of Leishmania major. Sandflies were trapped from animal burrows over a period of one year using castor oil-smeared sticky traps. Nineteen phlebotomine sandfly species were identified and their prevalence in this habitat determined. Dissections on the parous sandflies resulted in the isolation of Leishmania parasites from Phlebotomus martini and Sergentomyia garnhami. The isolated parasites were cultured in NNN medium and were consequently mass cultured in RPMI medium for biochemical characterisation. The parasites from S. garnhami were typed as Leishmania major.

Laboratory investigations on the survival and fecundity of Phlebotomus duboscqi (Diptera, Psychodidae), a vector of Leishmania major in Kenya.

The gonotrophic cycle, survival and reproductive potential of adult female Phlebotomus duboscqi, a vector of Leishmania major in Baringo District, Kenya was investigated in the laboratory. The sandflies were fed on hamster and apples as a sugar source and were placed in vials for oviposition. The feeding and care for oviposition was repeated for as long as the flies lived. The longest period P. duboscqi survived after taking the first blood meal was 45 days. The flies completed up to eight gonotropic cycles resulting into a very high fecundity rate. The implications of this in relation to disease transmission by P. duboscqi is discussed.

Application of polar-orbiting, meteorological satellite data to detect flooding of Rift Valley Fever virus vector mosquito habitats in Kenya.

Measurements of green-leaf vegetation dynamics recorded by the advanced very high resolution radiometer instruments onboard National Oceanic and Atmospheric Administration satellites 7 and 9 were used to derive ground moisture and rainfall patterns in Kenya and monitor resultant flooding of mosquito larval habitats (dambos) likely to support Rift Valley Fever virus vector mosquitoes (Aedes and Culex spp.). Satellite-derived data from mid-1981 to December 1988 have been analysed with corresponding rainfall, flooding and vector population data as they relate to Rift Valley Fever virus ecology. Single (7 x 7 km) and multiple grid-cell image analysis (200 x 300 km) in small localized areas and large geographical regions, respectively, of vegetation data were used to quantify the potential for flooding of mosquito breeding habitats. The ability to detect accurately parameters, such as ground moisture, that determine flooding could provide local officials with sufficient warning to allow for implementation of specific mosquito control measures before a disease outbreak.